For patients undergoing extended chemotherapeutic treatment the efficacy of platelet transfusion eventually fails because of 1) unmet massive needs, 2) platelet-bacterial-virus interaction and 3) development of resistance. The object is to overcome these obstacles in a directed and planned approach. First, the successful application of our pressure-freezing research on bioengineering principles will permit the stockpiling of platelets to meet the first problem. This intensive study will systematically add multiple preservatives and utilize in vitro end point of hypotonic stress, aggregometer and structural analysis. In vivo testing in a nonbleeding, non-infected absolutely thrombocytopenic model will provide immediate confirmation of prior in vitro testing. The second problem requires an extensive knowledge of the platelet bacterial interaction. The platelets role as a defense mechanism against bacterial infection will be explored as it affects neutrophil and monocyte chemotaxis and subsequent bacterial killing. Sepsis is a recognized significant factor in platelet transfusion failure. The study of platelets during these episodes will be done. Third, the potential effectiveness of prolonged plateletpheresis in producing younger platelets will be analyzed. Platelets from such a single donor will reduce incompatability. The efficiency of the latter will then be measured in a controlled clinical study. Several biochemical parameters (i.e. nucleotide, serotonin, lipid and enzymes) will be utilized in all these component parts. The physician, patient and physical elements for mounting these portions have been established with the prior support and are now coherently planned and related one to the other.